Targeting SLC3A2 subunit of system XC- is essential for m6A reader YTHDC2 to be an endogenous ferroptosis inducer in lung adenocarcinoma

The m⁶A reader YT521-B homology containing 2 (YTHDC2) has been identified to inhibit lung adenocarcinoma (LUAD) tumorigenesis by suppressing solute carrier 7A11 (SLC7A11)-dependent antioxidant function. SLC7A11 is a major functional subunit of system X_C^-. Inhibition of system X_C^- can induce ferroptosis. However, whether suppressing SLC7A11 is sufficient for YTHDC2 to be an endogenous ferroptosis inducer in LUAD is unknown. Here, we found that induction of YTHDC2 to a high level can induce ferroptosis in LUAD cells but not in lung and bronchus epithelial cells. In addition to SLC7A11, solute carrier 3A2 (SLC3A2), another subunit of system X_C^- was equally important for YTHDC2-induced ferroptosis. YTHDC2 m⁶A-dependently destabilized Homeo box A13 (HOXA13) mRNA because a potential m⁶A recognition site was identified within its 3' untranslated region (3'UTR). Interestingly, HOXA13 acted as a transcription factor to stimulate SLC3A2 expression. Thereby, YTHDC2 suppressed SLC3A2 via inhibiting HOXA13 in an m⁶A-indirect manner. Mouse experiments further confirmed the associations among YTHDC2, SLC3A2 and HOXA13, and demonstrated that SLC3A2 and SLC7A11 were both important for YTHDC2-impaired tumor growth and -induced lipid peroxidation in vivo. Moreover, higher expression of SLC7A11, SLC3A2 and HOXA13 indicate poorer clinical outcome in YTHDC2-suppressed LUAD patients. In conclusion, YTHDC2 is believed to be a powerful endogenous ferroptosis inducer and targeting SLC3A2 subunit of system X_C^- is essential for this process. Increasing YTHDC2 is an alternative ferroptosis-based therapy to treat LUAD.

Targeting SLC1A5 and SLC3A2/SLC7A5 as a Potential Strategy to Strengthen Anti-Tumor Immunity in the Tumor Microenvironment

Cancer cells are metabolically vigorous and are superior in the uptake of nutrients and in the release of the tumor microenvironment (TME)-specific metabolites. They create an acidic, hypoxic, and nutrient-depleted TME that makes it difficult for the cytotoxic immune cells to adapt to the metabolically hostile environment. Since a robust metabolism in immune cells is required for optimal anti-tumor effector functions, the challenges caused by the TME result in severe defects in the invasion and destruction of the established tumors. There have been many recent developments in NK and T cell-mediated immunotherapy, such as engineering them to express chimeric antigen receptors (CARs) to enhance tumor-recognition and infiltration. However, to defeat the tumor and overcome the limitations of the TME, it is essential to fortify these novel therapies by improving the metabolism of the immune cells. One potential strategy to enhance the metabolic fitness of immune cells is to upregulate the expression of nutrient transporters, specifically glucose and amino acid transporters. In particular, the amino acid transporters SLC1A5 and SLC7A5 as well as the ancillary subunit SLC3A2, which are required for efficient uptake of glutamine and leucine respectively, could strengthen the metabolic capabilities and effector functions of tumor-directed CAR-NK and T cells. In addition to enabling the influx and efflux of essential amino acids through the plasma membrane and within subcellular compartments such as the lysosome and the mitochondria, accumulating evidence has demonstrated that the amino acid transporters participate in sensing amino acid levels and thereby activate mTORC1, a master metabolic regulator that promotes cell metabolism, and induce the expression of c-Myc, a transcription factor essential for cell growth and proliferation. In this review, we discuss the regulatory pathways of these amino acid transporters and how we can take advantage of these processes to strengthen immunotherapy against cancer.

CD98-Mediated Adhesive Signaling Enables the Establishment and Propagation of Acute Myelogenous Leukemia

Acute myelogenous leukemia (AML) is an aggressive disease associated with drug resistance and relapse. To improve therapeutic strategies, it is critical to better understand the mechanisms that underlie AML progression. Here we show that the integrin binding glycoprotein CD98 plays a central role in AML. CD98 promotes AML propagation and lethality by driving engagement of leukemia cells with their microenvironment and maintaining leukemic stem cells. Further, delivery of a humanized anti-CD98 antibody blocks growth of patient-derived AML, highlighting the importance of this pathway in human disease. These findings indicate that microenvironmental interactions are key regulators of AML and that disrupting these signals with targeted inhibitors such as CD98 antibodies may be a valuable therapeutic approach for adults and children with this disease.

Decreased mRNA expression for the two subunits of system xc(-), SLC3A2 and SLC7A11, in WBC in patients with schizophrenia: Evidence in support of the hypo-glutamatergic hypothesis of schizophrenia

BACKGROUND

The cystine/glutamate antiporter system xc(-), playing a critical role in the regulation of glutamate release, might be implicated in the pathogenesis of schizophrenia. This study examined whether peripheral expressions of the system xc(-) subunits are characteristic of schizophrenia.

METHODS

Expression of system xc(-) genes including SLC3A2 and SLC7A11 in peripheral WBCs of patients with schizophrenia and healthy individuals were measured using quantitative PCR. Both psychotropic-free and medicated patients with schizophrenia were recruited.

RESULTS

A total of 96 schizophrenia patients (48 medicated and 48 drug-free) and 96 healthy individuals were enrolled. The mRNA expression levels using the 2(-ΔΔC)T Method of both SLC3A2 and SLC7A11 in WBCs of schizophrenia patients were markedly lower than that of healthy individuals (0.22 and 0.48, respectively, the mRNA expression level of normal controls was normalized to 1). There was no significant difference between medicated and drug-free patients in the mRNA expressions of both SLC3A2 and SLC7A11. The Receiver Operating Characteristics (ROC) analysis of SLC3A2 mRNA levels using ΔΔCT values for drug-free schizophrenia patients vs. healthy controls determined an optimal cutoff value, 0.801, with high sensitivity (1.000) and modest specificity (0.694) (area under curve of ROC = 0.794).

CONCLUSION

This is the first study indicating that the peripheral mRNA expression levels of SLC7A11 and SLC3A2 may be lower in patients with schizophrenia than healthy individuals. The finding supports the hypo-glutamatergic neurotransmission hypothesis in schizophrenia. Whether mRNA expression of system xc(-) subunits genes, particularly SLC3A2, could serve as a potential biomarker of schizophrenia needs further studies.

Exosomal miR-142-3p secreted by hepatitis B virus (HBV)-hepatocellular carcinoma (HCC) cells promotes ferroptosis of M1-type macrophages through SLC3A2 and the mechanism of HCC progression

BACKGROUND

Most patients with hepatitis B virus (HBV) infection will develop hepatocellular carcinoma (HCC). This study aimed to explore the potential mechanism of miR-142-3p in HCC caused by HBV infection.

METHODS

HepG2 cells and M1 macrophages were cocultured and then infected with HBV to establish an in vitro model. MicroRNA (miRNA) and messenger RNA (mRNA) expression was analyzed by quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western blot. The protein expressions of COX2, ACSL4, PTGS2, GPX4, and NOX1 were analyzed by Western blot. Flow cytometry and TUNEL assays were used to assess cell reactive oxygen species (ROS) and ferroptosis, respectively. Cell invasion and migration were measured by Transwell assay. To evaluate the ferroptosis of M1-type macrophages, glutathione (GSH), malondialdehyde (MDA), and Fe2+ content was detected by corresponding kits. Dual luciferase reporter gene detection verified the targeting relationship between miR-142-3p and SLC3A2.

RESULTS

MiR-142-3p was highly expressed in HBV-infected HCC patients and HBV-infected M1-type macrophages. Inhibition of miR-142-3p or overexpression of SLC3A2 reversed ferroptosis and inhibited the proliferation, migration, and invasion of HCC cells.

CONCLUSIONS

Our findings indicated that miR-142-3p promoted HBV-infected M1-type macrophage ferroptosis through SLC3A2, affecting the production of GSH, MDA, and Fe2+ and accelerating the development of HCC. The regulation of miR-142-3p and its target genes will help to clarify the pathogenesis of HCC induced by HBV infection and provide new theoretical foundations and therapeutic targets.

SLC3A2 promotes tumor-associated macrophage polarization through metabolic reprogramming in lung cancer

Tumor-associated macrophages (TAMs) are one of the most abundant immunosuppressive cells in the tumor microenvironment and possess crucial functions in facilitating tumor progression. Emerging evidence indicates that altered metabolic properties in cancer cells support the tumorigenic functions of TAMs. However, the mechanisms and mediators the underly the cross-talk between cancer cells and TAMs remain largely unknown. In the present study, we revealed that high solute carrier family 3 member 2 (SLC3A2) expression in lung cancer patients was associated with TAMs and poor prognosis. Knockdown of SLC3A2 in lung adenocarcinoma cells impaired M2 polarization of macrophages in a coculture system. Using metabolome analysis, we identified that SLC3A2 knockdown altered the metabolism of lung cancer cells and changed multiple metabolites, including arachidonic acid, in the tumor microenvironment. More importantly, we showed that arachidonic acid was responsible for SLC3A2-mediated macrophage polarization in the tumor microenvironment to differentiate into M2 type both in vitro and in vivo. Our data illustrate previously undescribed mechanisms responsible for TAM polarization and suggest that SLC3A2 acts as a metabolic switch on lung adenocarcinoma cells to induce macrophage phenotypic reprogramming through arachidonic acid.

Identification of AR-V7 downstream genes commonly targeted by AR/AR-V7 and specifically targeted by AR-V7 in castration resistant prostate cancer

Primary prostate cancer (PC) progresses to castration-resistant PC (CRPC) under androgen deprivation therapy, by mechanisms e.g. expression of androgen receptor (AR) splice variant-7 (AR-V7). Here we conducted comprehensive epigenome and transcriptome analyses comparing LNCaP, primary PC cells, and LNCaP95, AR-V7-expressing CRPC cells derived from LNCaP. Of 399 AR-V7 target regions identified through ChIP-seq analysis, 377 could be commonly targeted by hormone-stimulated AR, and 22 were specifically targeted by AR-V7. Among genes neighboring to these AR-V7 target regions, 78 genes were highly expressed in LNCaP95, while AR-V7 knockdown led to significant repression of these genes and suppression of growth of LNCaP95. Of the 78 AR-V7 target genes, 74 were common AR/AR-V7 target genes and 4 were specific AR-V7 target genes; their most suppressed genes by AR-V7 knockdown were NUP210 and SLC3A2, respectively, and underwent subsequent analyses. NUP210 and SLC3A2 were significantly upregulated in clinical CRPC tissues, and their knockdown resulted in significant suppression of cellular growth of LNCaP95 through apoptosis and growth arrest. Collectively, AR-V7 contributes to CRPC proliferation by activating both common AR/AR-V7 target and specific AR-V7 target, e.g. NUP210 and SLC3A2.

ZEB1 Promotes Chemoresistance to Cisplatin in Ovarian Cancer Cells by Suppressing SLC3A2

Ovarian cancer is one of the deadliest gynecological malignancies in women. Chemoresistance has been a major obstacle for ovarian cancer treatment. Zinc finger E-box-binding homeobox 1 (ZEB1) is an important regulator of tumor development in various types of cancer. Abnormal expression of SLC3A2 (CD98hc), a type 2 transmembrane cell surface molecule, has been described in several cancers. This study was designed to investigate the role of ZEB1 and SLC3A2 in the chemoresistance to cisplatin in ovarian cancer cells. We found that ZEB1 was increased in cisplatin-resistant SKOV3/DPP cells. Downregulation of ZEB1 significantly decreased cell viability in response to cisplatin, increased cis-platin-induced apoptosis, and decreased migration and invasion in the presence of cisplatin. In addition, downregulation of ZEB1 decreased the volume and weight of implanted tumors. SLC3A2 was decreased in cisplatin-resistant SKOV3/DPP cells. Upregulation of SLC3A2 significantly decreased cell viability in response to cisplatin, increased cisplatin-induced apoptosis, and decreased migration and invasion in the presence of cisplatin. Moreover, upregulation of SLC3A2 decreased the volume and weight of implanted tumors. Downregulation of ZEB1 resulted in a significant increase of SLC3A2 expression. Moreover, downregulation of SLC3A2 significantly inhibited ZEB1 knockdown-mediated inhibition of cisplatin-resistance. ZEB1-mediated regulation of SLC3A2 was involved in the chemoresistance to cisplatin in ovarian cancer cells. Overall, we provide new insights into the mechanism of chemoresistance to cisplatin in ovarian cancer cells. ZEB1/SLC3A2 may be promising therapeutic targets for enhancement of the sensitivity of ovarian cancer cells to cisplatin-mediated chemotherapy.

Co-Expression Effect of SLC7A5/SLC3A2 to Predict Response to Endocrine Therapy in Oestrogen-Receptor-Positive Breast Cancer

The majority of breast cancers are oestrogen-receptor-positive (ER+) and are subject to endocrine therapy; however, an unpredictable subgroup of patients will develop resistance to endocrine therapy. The SLC7A5/SLC3A2 complex is a major route for the transport of large neutral essential amino acids through the plasma membrane. Alterations in the expression and function of those amino-acid transporters lead to metabolic reprogramming, which contributes to the tumorigenesis and drug resistance. This study aims to assess the effects and roles of SLC7A5/SLC3A2 co-expression in predicting responses to endocrine therapy in patients with ER+ breast cancer. The biological and clinical impact of SLC7A5/SLC3A2 co-expression was assessed in large annotated cohorts of ER+/HER2− breast cancer with long-term follow-up at the mRNA and protein levels. In vitro experiments were conducted to investigate the effect of SLC7A5/SLC3A2 knockdown in the proliferation of cancer cells and to the sensitivity to tamoxifen. We found that proliferation-related genes are highly expressed in a subgroup of patients with high SLC7A5/SLC3A2, and knockdown of SLC7A5/SLC3A2 decreased proliferation of ER+ breast cancer cells. In patients treated with endocrine therapy, high SLC7A5/SLC3A2 co-expression was associated with poor patient outcome, and depletion of SLC7A5/SLC3A2 using siRNA increased the sensitivity of breast cancer cells to tamoxifen. On the basis of our findings, SLC7A5/SLC3A2 co-expression has the potential of identifying a subgroup of ER+/HER2− breast cancer patients who fail to benefit from endocrine therapy and could guide the choice of other alternative therapies.

Methylmercury Uptake into BeWo Cells Depends on LAT2-4F2hc, a System L Amino Acid Transporter

The organic mercury compound methylmercury (MeHg) is able to target the fetal brain. However, the uptake of the toxicant into placental cells is incompletely understood. MeHg strongly binds to thiol-S containing molecules such as cysteine. This MeHg-l-cysteine exhibits some structural similarity to methionine. System L plays a crucial role in placental transport of essential amino acids such as leucine and methionine and thus has been assumed to also transport MeHg-l-cysteine across the placenta. The uptake of methylmercury and tritiated leucine and methionine into the choriocarcinoma cell line BeWo was examined using transwell assay and small interfering (si)RNA mediated gene knockdown. Upon the downregulation of large neutral amino acids transporter (LAT)2 and 4F2 cell-surface antigen heavy chain (4F2hc), respectively, the levels of [³H]leucine in BeWo cells are significantly reduced compared to controls treated with non-targeting siRNA (p < 0.05). The uptake of [³H]methionine was reduced upon LAT2 down-regulation as well as methylmercury uptake after 4F2hc silencing (p < 0.05, respectively). These findings suggest an important role of system L in the placental uptake of the metal. Comparing the cellular accumulation of mercury, leucine, and methionine, it can be assumed that (1) MeHg is transported through system L amino acid transporters and (2) system L is responsible for the uptake of amino acids and MeHg primarily at the apical membrane of the trophoblast. The findings together can explain why mercury in contrast to other heavy metals such as lead or cadmium is efficiently transported to fetal blood.

The combined expression of solute carriers is associated with a poor prognosis in highly proliferative ER+ breast cancer

PURPOSE

Breast cancer (BC) is a heterogeneous disease characterised by variant biology, metabolic activity, and patient outcome. Glutamine availability for growth and progression of BC is important in several BC subtypes. This study aimed to evaluate the biological and prognostic role of the combined expression of key glutamine transporters, SLC1A5, SLC7A5, and SLC3A2 in BC with emphasis on the intrinsic molecular subtypes.

METHODS

SLC1A5, SLC7A5, and SLC3A2 were assessed at the protein level, using immunohistochemistry on tissue microarrays constructed from a large well-characterised BC cohort (n = 2248). Patients were stratified into accredited clusters based on protein expression and correlated with clinicopathological parameters, molecular subtypes, and patient outcome.

RESULTS

Clustering analysis of SLC1A5, SLC7A5, and SLC3A2 identified three clusters low SLCs (SLC1A5-/SLC7A5-/SLC3A2-), high SLC1A5 (SLC1A5+/SLC7A5-/SLC3A2-), and high SLCs (SLC1A5+/SLC7A5+/SLC3A2+) which had distinct correlations to known prognostic factors and patient outcome (p < 0.001). The key regulator of tumour cell metabolism, c-MYC, was significantly expressed in tumours in the high SLC cluster (p < 0.001). When different BC subtypes were considered, the association with the poor outcome was observed in the ER+ high proliferation/luminal B class only (p = 0.003). In multivariate analysis, SLC clusters were independent risk factor for shorter BC-specific survival (p = 0.001).

CONCLUSION

The co-operative expression of SLC1A5, SLC7A5, and SLC3A2 appears to play a role in the aggressive subclass of ER+ high proliferation/luminal BC, driven by c-MYC, and therefore have the potential to act as therapeutic targets, particularly in synergism.

MIF/SCL3A2 depletion inhibits the proliferation and metastasis of colorectal cancer cells via the AKT/GSK-3β pathway and cell iron death

This study investigated the mechanisms of migration inhibitory factor (MIF) and solute carrier family 3 member 2 (SLC3A2) in colorectal cancer progression. The levels of MIF and SLC3A2 expression in cells were measured by RT-qPCR. SW480 and SW620 cells were transfected with sh-MIF and sh-SLC3A2, respectively. MIF, SLC3A2, GPX4, E-cadherin and N-cadherin expression were detected by immunofluorescence (IF). CCK8 and Transwell assays were performed to detect cell proliferation and migration. Co-immunoprecipitation (CoIP) was used to measure the binding activity of MIF and SLC3A2. Finally, a nude mouse tumorigenicity assay was used to confirm the functions of MIF and SLC3A2 in colorectal cancer. Results showed that the levels of MIF and SLC3A2 expression were up-regulated in colorectal cancer cells. Inhibition of MIF or SLC3A2 expression prevented cell proliferation, migration, epithelial-mesenchymal transition (EMT) and invasion. In addition, knockdown of MIF and SLC3A2 promoted iron death in SW480 and SW620 cells. CoIP results showed that MIF and SLC3A2 directly interact with each other. Knockdown of both MIF and SLC3A2 inhibited tumour growth and metastasis via the AKT/GSK-3β pathway in vivo. The Akt/GSK-3β pathway was found to participate in regulating MIF and SLC3A2 both in vivo and in vitro. MIF and SLC3A2 might be potential biomarkers for monitoring the treatment of colorectal cancer.

LAT1 (SLC7A5) and CD98hc (SLC3A2) complex dynamics revealed by single-particle cryo-EM

Solute carriers are a large class of transporters that play key roles in normal and disease physiology. Among the solute carriers, heteromeric amino-acid transporters (HATs) are unique in their quaternary structure. LAT1-CD98hc, a HAT, transports essential amino acids and drugs across the blood-brain barrier and into cancer cells. It is therefore an important target both biologically and therapeutically. During the course of this work, cryo-EM structures of LAT1-CD98hc in the inward-facing conformation and in either the substrate-bound or apo states were reported to 3.3-3.5 Å resolution [Yan et al. (2019), Nature (London), 568, 127-130]. Here, these structures are analyzed together with our lower resolution cryo-EM structure, and multibody 3D auto-refinement against single-particle cryo-EM data was used to characterize the dynamics of the interaction of CD98hc and LAT1. It is shown that the CD98hc ectodomain and the LAT1 extracellular surface share no substantial interface. This allows the CD98hc ectodomain to have a high degree of movement within the extracellular space. The functional implications of these aspects are discussed together with the structure determination.

Defining the role of polyamines in colon carcinogenesis using mouse models

Genetics and diet are both considered important risk determinants for colorectal cancer, a leading cause of death in the US and worldwide. Genetically engineered mouse (GEM) models have made a significant contribution to the characterization of colorectal cancer risk factors. Reliable, reproducible, and clinically relevant animal models help in the identification of the molecular events associated with disease progression and in the development of effictive treatment strategies. This review is focused on the use of mouse models for studying the role of polyamines in colon carcinogenesis. We describe how the available mouse models of colon cancer such as the multiple intestinal neoplasia (Min) mice and knockout genetic models facilitate understanding of the role of polyamines in colon carcinogenesis and help in the development of a rational strategy for colon cancer chemoprevention.

HCMV-miR-US33-5p promotes apoptosis of aortic vascular smooth muscle cells by targeting EPAS1/SLC3A2 pathway

BACKGROUND

In patients with acute aortic dissection (AAD), increased vascular smooth muscle cell (VSMC) apoptosis has been found. Human cytomegalovirus (HCMV)-miR-US33-5p was significantly increased in the plasma of patients with AAD. However, the roles of miR-US33-5p in human aortic VSMC (HA-VSMC) apoptosis remain to be elucidated.

METHODS

In the current study, cell apoptosis was analyzed by flow cytometry, cell proliferation by CCK-8 assay, and differentially expressed genes by RNA sequencing. Luciferase reporter assay was used for binding analysis between miR-US33-5p and endothelial PAS domain protein 1 (EPAS1), and EPAS1 and amino acid transporter heavy chain, member 2 (SLC3A2). The enrichment degree of SLC3A2 promoter DNA was analyzed by chromatin immunoprecipitation assay. Quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and immunoblotting were performed for measuring messenger RNA (mRNA) and protein levels, respectively.

RESULTS

It was found that HCMV infection inhibited proliferation but promoted HA-VSMC apoptosis by upregulating HCMV-miR-US33-5p. Transfection of HCMV-miR-US33-5p mimics the significant effect on several signaling pathways including integrin signaling as shown in the RNA sequencing data. Western blotting analysis confirmed that HCMV-miR-US33-5p mimics suppression of the activity of key factors of the integrin signal pathway including FAK, AKT, CAS, and Rac. Mechanistic study showed that HCMV-miR-US33-5p bound to the 3'-untranslated region of EPAS1 to suppress its expression, leading to suppression of SLC3A2 expression, which ultimately promoted cell apoptosis and inhibited cell proliferation. This was confirmed by the findings that silencing EPAS1 significantly reduced the SLC3A2 expression and inhibited proliferation and key factors of integrin signal pathway.

CONCLUSIONS

HCMV-miR-US33-5p suppressed proliferation, key factors of integrin signal pathway, and EPAS1/SLC3A2 expression, but promoted HA-VSMC apoptosis. These findings highlighted the importance of HCMV-miR-US33-5p/EPAS1/SCL3A2 signaling and may provide new insights into therapeutic strategies for AAD.

SLC3A2, antigen of mAb 3G9, promotes migration and invasion by upregulating of mucins in gastric cancer

Solute carrier family 3 member 2 (SLC3A2) has been reported to be highly expressed in a variety of carcinomas. However, the function of SLC3A2 in gastric carcinoma (GC) has not been well explored. Monoclonal antibody (mAb) 3G9, generated from immunogen of various human GC cell lines, has been shown to bind to GC tissues specifically. In this study, we identified the target antigen of mAb 3G9 as SLC3A2, and detected the expression profile of SLC3A2 in a panel of gastric cancer cell lines and GC tumor tissues. We found that the increased expression of SLC3A2 was associated with serosal invasion in GC patients. Knockout of SLC3A2 suppressed the migration and invasion of BGC-823 cells in vitro and in vivo, whereas overexpression of SLC3A2 in NCI-N87 cells promoted the migration and invasion in vitro and in vivo. Mechanistic investigations suggested that MUC1, MUC16 and MUC5B were the downstream genes of SLC3A2 in GC cells. Taken together, our data suggested that SLC3A2 promoted the aggressive phenotype of GC by upregulating several mucin genes expression and may serve as a potential biomarker for diagnosis and target therapy.

Identification of the target protein and molecular mechanism of honokiol in anti-inflammatory action

BACKGROUND

Searching the targets of natural products is very important for drug discovery and elucidating the mechanism of drug action and disease. Honokiol (HK), as the major active component of Magnolia officinalis Rehder & E.H.Wilson, has been widely used in medicine and cosmetics. Among its bioactivities, its anti-inflammatory activity is particularly impressive. However, the target protein of HK in anti-inflammatory action and its regulatory mechanism are unclear.

PURPOSE

Here, we identified the target protein and molecular mechanism of the anti- inflammatory action of HK.

METHODS

First, an LPS-induced septic shock model and DSS-induced ulcerative colitis model were used to assess the anti-inflammatory efficacy of HK. Second, the drug affinity responsive target stability, proteomics analysis, thermal shift assays and cellular thermal shift assays were used to identify and validate the target of HK. Finally, western blot, ELISA, LDH immunofluorescence staining, shRNA and LC/MS for L-leucine analysis were performed to determine the mechanism of the anti-inflammatory action of HK.

RESULTS

This study revealed that HK significantly alleviated LPS-induced septic shock and DSS-induced ulcerative colitis in vivo, suggesting that HK has significant anti-inflammatory activity. HK treatment dramatically reduced IL-1β release and caspase-1 activation at different time points, showing that HK could inhibit both NLRP3 inflammasome priming and activation processes in cells. HK also suppressed adaptor apoptosis speck-like protein oligomerization. Mechanistically, SLC3A2 was identified as a direct target of HK in THP-1 cells. HK downregulated SLC3A2 expression by promoting its degradation via proteasome-mediated proteolysis. Further study demonstrated that HK triggered SLC3A2 to suppress NLRP3 inflammasome activation by significantly reducing the content of L-leucine transported into cells and lysosomes to block the mTORC1 pathway.

CONCLUSIONS

Our work identified HK as a promising anti-inflammatory drug candidate through the SLC3A2/L-leucine/mTORC1/NLRP3 pathways.

Anti-proliferation and anti-migration effects of Yishen Tongbi decoction in experimental rheumatoid arthritis by suppressing SLC3A2/integrin β3 signaling pathways

BACKGROUND

Yishen Tongbi (YSTB) decoction is a patented herbal formula that is used in China to treat rheumatoid arthritis (RA); however, the exact mechanism of its anti-synovial hyperplasia efficacy has not been fully elucidated.

PURPOSE

Based on our previous proteomics study, we aimed to reveal whether YSTB inhibits the proliferation and migration of RA-FLSs through the SLC3A2/integrin β3 pathway in vivo and in vitro.

STUDY DESIGN

The study design consists of three parts, a comparison of the expression of SLC3A2 and integrin β3 in synovial tissues of RA and OA patients; an animal experiment to verify the pharmacodynamic effect of YSTB, and in vitro experiment to elucidate the specific mechanism of YSTB.

METHODS

The expression of SLC3A2 and integrin β3 in the synovial tissues of patients with RA and osteoarthritis (OA) patients were detected by immunohistochemistry (IHC). In vitro, firstly, the proliferation and migration abilities of HFLS (human fibroblast-like synoviocytes) and HFLS-RA (human fibroblast-like synoviocytes-RA) cells were compared by EdU staining and wound healing assays, respectively, and the differences in the expression and localization of SLC3A2, integrin β3, p-FAK and p-Src between HFLS and HFLS-RA cells were detected by IF and WB. In vivo, DBA/1 mice were injected with bovine collagen II to construct a CIA mouse model. Paw swelling, body weight and the arthritis index (AI) were used as basic treatment evaluation indicators for YSTB. Micro-CT and histopathological analyses of the knee and ankle joints were also performed. In addition, the expression of SLC3A2, integrin β3, p-FAK and p-Src in the synovial tissue of mice was detected by IHC. Subsequently, CCK-8 was used to screen for suitable concentrations of YSTB for use in HFLS-RA cells. EdU staining and transwell migration assays were performed to evaluate the inhibitory effect of YSTB on cell proliferation and migration, and WB was conducted to assess whether YSTB inhibited HFLS-RA migration through downregulation of the SLC3A2/integrin β3 pathways.

RESULTS

IHC showed that the expression of SLC3A2 and integrin β3 was higher in RA synovial tissues than in OA tissues. In vivo experiments showed that YSTB inhibited synovial hyperplasia, prevented bone destruction, and reduced the expression of SLC3A2, integrin β3, p-FAK and p-Src. In vitro experiments showed that YSTB inhibited HFLS-RA migration and proliferation by inhibiting the expression of SLC3A2/integrin β3 and downstream signaling molecules.

CONCLUSION

YSTB inhibits the proliferation and migration of synovial fibroblasts in RA by downregulating the SLC3A2/integrin β3 pathways.

Integrated analysis of FKBP1A/SLC3A2 axis in everolimus inducing ferroptosis of breast cancer and anti-proliferation of T lymphocyte

Background: Solute Carrier Family 3 Member 2 (SLC3A2) is a member of the solute carrier family that plays pivotal roles in regulation of intracellular calcium levels and transports L-type amino acids. However, there are insufficient scientific researches on the prognostic and immunological roles of SLC3A2 in breast cancer (BC) and whether everolimus regulates novel SLC3A2 related molecular mechanism in the immuno-oncology context of the tumor microenvironment (TME), therefore, we see a necessity to conduct the current in silico and biological experimental study. Methods: Using diverse online databases, we investigated the role of SLC3A2 in therapy response, clinicopathological characteristics, tumor immune infiltration, genetic alteration, methylation and single cell sequencing in BC. WB, Co-IP, cell proliferation assay, Edu staining, ROS and GSH assay and in vivo tumor xenograft assays were performed to verify FKBP1A/SLC3A2 axis in everolimus inducing ferroptosis of breast cancer. Co-cultures and IL-9 ELISA were performed to demonstrate the T lymphocyte function. Results: We demonstrated that SLC3A2 was aberrantly expressed among various BC cohorts. Our results also suggested that SLC3A2 expression was associated with chemotherapeutic outcome in BC patients. Our results further indicated that SLC3A2 was associated with tumor infiltration of cytotoxic T cell but not other immune cells among BC TME. The alterations in SLC3A2 gene had a significant correlation to relapse free survival and contributed a significant impact on BC tumor mutational burden. Finally, SLC3A2 was illustrated to be expressed in diverse BC cellular populations at single cell level, and negatively linked to angiogenesis, inflammation and quiescence, but positively correlated with other functional phenotypes. Noteworthily, everolimus (a targeted therapy drug for BC) related protein, FK506-binding protein 1A (FKBP1A) was found to bind with SLC3A2, and negatively regulated SLC3A2 expression during the processes of everolimus inducing ferroptosis of BC cells and promoting anti-proliferation of Th9 lymphocytes. Conclusions: Altogether, our study strongly implies that SLC3A2 is an immuno-oncogenic factor and FKBP1A/SLC3A2 axis would provide insights for a novel immunotherapy approach for the treatment of BC in the context of TME.

SLC3A2, as an indirect target gene of ALDH2, exacerbates alcohol-associated liver cancer via the sphingolipid biosynthesis pathway

Excessive drinking is one of the main causes of liver cancer. In the process of alcohol metabolism, aldehyde dehydrogenase 2 (ALDH2) is the key enzyme of acetaldehyde metabolism. ALDH2 gene deficiency is positively associated with the risk of hepatocellular carcinoma (HCC). However, no studies have shown a connection between ALDH2 and another metabolic regulatory gene, SLC3A2. In this study, we analyzed the expression levels of ALDH2 and SLC3A2 in liver cancer tissues based on the TCGA database. Subsequently, we constructed ALDH2 knockout and SLC3A2 knock-in transgenic mice to check the roles of ALDH2 and SLC3A2 in tumorigenesis in vivo. In addition, we examined the mechanisms of ALDH2 and SLC3A2 in HCC cells using small RNA interference technology. Consistent with previous studies, we also confirmed the functions of ALDH2 in inhibiting hepatocarcinogenesis, while SLC3A2 had the opposite effect. The main finding of this study is that ALDH2 inhibited BSG expression through the TGF-β1 pathway, which indirectly inhibited SLC3A2 expression; subsequently, the sphingolipid metabolism pathway was also inhibited in HCC cells. Therefore, SLC3A2 is a novel target for HCC treatment.

Examining xCT-mediated selenium uptake and selenoprotein production capacity in cells

The production of selenoproteins in cancer cells is dependent on uptake of selenium and processing via the selenocysteine biosynthesis pathway. Both the uptake and processing of selenium has recently shown to be upregulated in subsets of cancer cells due to their increased expression of xCT transporter, and the resulting increased expression of selenoproteins such as GPX4 can play multiple roles in cancer cells such as providing protection against ferroptotic insults. Here, we describe a set of protocols designed to measure this process in cancer cell culture-the measurement of xCT transporter expression and activity, the intracellular uptake of selenium in cancer cells, and the expression of selenoproteins as the final functional readout of this process. The successful measurement of xCT requires non-denaturing western blotting of xCT subunits, while its activity is determined by the measurement of reduced thiol groups that accumulate over time, as determined by Ellman's reagent. Selenium uptake is determined by supplementing a selenium source and then measuring total intracellular selenium levels, which is determined from digested cellular material using a reactive fluorescent probe or via inductively coupled plasma mass spectrometry. Finally, specific tips for efficiently determining the expression level of a set of "indicator" selenoproteins is provided. These parameters allow one to determine the "selenophilicity" of cells, i.e., the ability of cells to utilize selenite to upregulate their selenoprotein production and thus antioxidant defenses.

Validation of CD98hc as a Therapeutic Target for a Combination of Radiation and Immunotherapies in Head and Neck Squamous Cell Carcinoma

Most patients with head and neck squamous cell carcinomas (HNSCC) are diagnosed at a locally advanced stage and show heterogeneous treatment responses. Low SLC3A2 (solute carrier family 3 member 2) mRNA and protein (CD98hc) expression levels are associated with higher locoregional control in HNSCC patients treated with primary radiochemotherapy or postoperative radiochemotherapy, suggesting that CD98hc could be a target for HNSCC radiosensitization. One of the targeted strategies for tumor radiosensitization is precision immunotherapy, e.g., the use of chimeric antigen receptor (CAR) T cells. This study aimed to define the potential clinical value of new treatment approaches combining conventional radiotherapy with CD98hc-targeted immunotherapy. To address this question, we analyzed the antitumor activity of the combination of fractionated irradiation and switchable universal CAR (UniCAR) system against radioresistant HNSCC cells in 3D culture. CD98hc-redirected UniCAR T cells showed the ability to destroy radioresistant HNSCC spheroids. Also, the infiltration rate of the UniCAR T cells was enhanced in the presence of the CD98hc target module. Furthermore, sequential treatment with fractionated irradiation followed by CD98hc-redirected UniCAR T treatment showed a synergistic effect. Taken together, our obtained data underline the improved antitumor effect of the combination of radiotherapy with CD98hc-targeted immunotherapy. Such a combination presents an attractive approach for the treatment of high-risk HNSCC patients.

m6A modification mediates SLC3A2/SLC7A5 translation in 3-methylcholanthrene-induced uroepithelial transformation

3-Methylcholanthracene (3-MC) is one of the most carcinogenic polycyclic aromatic hydrocarbons (PAHs). Long-term exposure to PAHs has been thought of as an important factor in urothelial tumorigenesis. N6-methyladenosine (m6A) exists widely in eukaryotic organisms and regulates the expression level of specific genes by regulating mRNA stability, translation efficiency, and nuclear export efficiency. Currently, the potential molecular mechanisms that regulate m6A modification for 3-MC carcinogenesis remain unclear. Here, we profiled mRNA, m6A, translation and protein level using "-omics" methodologies, including transcriptomes, m6A profile, translatomes, and proteomics in 3-MC-transformed urothelial cells and control cells. The key molecules SLC3A2/SLC7A5 were screened and identified in 3-MC-induced uroepithelial transformation. Moreover, SLC7A5/SLC3A2 promoted uroepithelial cells malignant phenotype in vitro and in vivo. Mechanically, METTL3 and ALKBH5 mediated m6A modification of SLC3A2/SLC7A5 mRNA in 3-MC-induced uroepithelial transformation by upregulating the translation of SLC3A2/SLC7A5. Furthermore, programmable m6A modification of SLC3A2/SLC7A5 mRNA affected the expression of its proteins. Taken together, our results revealed that the m6A modification-mediated SLC3A2/SLC7A5 translation promoted 3-MC-induced uroepithelial transformation, suggesting that targeting m6A modification of SLC3A2/SLC7A5 may be a potential therapeutic strategy for bladder cancer related to PAHs.

Bispecific antibody shuttles targeting CD98hc mediate efficient and long-lived brain delivery of IgGs

The inability of antibodies to penetrate the blood-brain barrier (BBB) is a key limitation to their use in diverse applications. One promising strategy is to deliver IgGs using a bispecific BBB shuttle, which involves fusing an IgG to a second affinity ligand that engages a cerebrovascular endothelial target and facilitates transport across the BBB. Nearly all prior efforts have focused on shuttles that target transferrin receptor (TfR-1) despite inherent delivery and safety challenges. Here, we report bispecific antibody shuttles that engage CD98hc, the heavy chain of the large neutral amino acid transporter (LAT1), and efficiently transport IgGs into the brain. Notably, CD98hc shuttles lead to much longer-lived brain retention of IgGs than TfR-1 shuttles while enabling more specific targeting due to limited CD98hc engagement in the brain parenchyma, which we demonstrate for IgGs that either agonize a neuronal receptor (TrkB) or target other endogenous cell-surface proteins on neurons and astrocytes.